Examine source code of History Master

{
  "name": "History Master",
  "version": "2.1.6",
  "description": "Visualize browsing history, Discover your unknown habits.",
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "options_ui": {
    "page": "option/index.html",
    "chrome_style": false,
    "open_in_tab": true
  },
  "browser_action": {
    "browser_style": true,
    "default_icon": {
      "16": "option/images/16.png",
      "32": "option/images/32.png",
      "64": "option/images/64.png",
      "128": "option/images/128.png"
    },
    "default_title": "History Master"
  },
  "icons": {
    "16": "option/images/16.png",
    "32": "option/images/32.png",
    "64": "option/images/64.png",
    "128": "option/images/128.png"
  },
  "permissions": [
    "history",
    "tabs",
    "downloads"
  ],
  "content_security_policy": "default-src 'self'; font-src https://*; style-src 'self'  'unsafe-inline'",
  "manifest_version": 2
}